Method of manufacturing a speed gear and an apparatus for manufacturing a speed gear

ABSTRACT

Speed gear are manufactured by integrally molding, by either hot or warm forging, a speed gear section and a clutch spline section. Teeth of the speed gear in the speed gear section and an involute spline parallel to an axial line of the gear in the clutch spline section are rough formed. The involute spline parallel to the axial line of gear formed on the section of clutch spline is formed, by cold forging, into an involute spline with a back taper having a chamfer at the tip. The teeth of the speed gear formed at the speed gear section are finish formed by forming the speed gear teeth by rolling dies, by cold forging, while turning them around a shaft hole with reference to the clutch spline section forming the involute spline with back taper. A speed gear having a speed gear section and a clutch spline section including speed gear teeth and an involute spline with a back taper having a chamfer at the tip is thereby provided.

This is a Divisional Application of U.S. patent application Ser. No.09/468,089 filed Dec. 21, 1999 which in turn is a Divisional Applicationof U.S. patent application Ser. No. 09/058,846 filed Apr. 13, 1998.

BACKGROUND OF THE INVENTION

The present invention relates to a speed gear having a speed gearsection and a clutch spline section mainly used for a transmissiongearbox, and a manufacturing method and apparatus for the speed gear.

Conventionally, a speed gear having a speed gear section and a clutchspline section used for a transmission gearbox is manufactured bymethods such as:

1. A method which comprises forming a speed gear section and splineteeth respectively by submitting a speed gear section and a clutchspline section, integrally molded by hot forging, to machining such ashobbing, etc;

2. A method which comprises forming a speed gear section by submitting aspeed gear section molded by hot forging to machining such as hobbing,etc., and integrating the speed gear section and a clutch spline sectionhaving spline teeth molded by cold forging by either spline connectionor electron beam welding; and

3. A method which comprises forming a speed gear section by submitting aspeed gear section and a clutch spline section integrally molded by hotforging to machining such as hobbing, etc. and forming a clutch splinesection by hot forging and cold forging, respectively.

By the way, methods 1 to 3 all consist in forming the speed gear sectionby submitting the speed gear section to machining such as hobbing, etc.For that reason, they had a problem in that the metal flow of thesection of speed gear was cut off, not only reducing the strength of thegear but also inevitably leading to an increase of the manufacturingcost due to machining.

As a solution to this problem, adoption of a method for forming speedgear teeth in the speed gear section by cold forging with a press may beconceivable, but no high-accuracy speed gear section could bemanufactured because of the difficulty of securing concentricity betweenthe clutch spline section and the speed gear section forming speed gearteeth.

Moreover, a speed gear W generally used for the transmission gearbox atpresent is provided, as shown in FIG. 11, with speed gear section Pa andclutch spline section Pb, forming helical teeth Ga as speed gear teethat the speed gear section Pa and an involute spline with a back taper Gbhaving a chamfer Cb at the tip of the clutch spline section Pb,respectively.

The helical teeth Ga formed at the speed gear section Pa generally have,as shown in FIG. 10 (C), a torsional angle α of 15° to 35° on the rightor on the left, and are formed as high teeth to reduce the gear noiseproduced during high-speed rotation of the speed gear W.

For that reason, in the case where an attempt is made to form helicalteeth Ga by cold forging with a press, for example, the greater part ofthe forming pressure must be supported by the tooth flank Fa of thehelical teeth Ga. This causes deflection of the helical teeth Ga,producing a gap in the tooth flank Fb and inducing the material to flowinto that gap.

As a result, the helical teeth Ga are formed differently at thetorsional angle α of the tooth flank Fa and the torsional angle α b ofthe tooth flank Fb, making it difficult to manufacture a speed gear ofhigh accuracy. In addition, since this trend becomes particularlyconspicuous as the torsional angle a gets larger, it was impossible toform helical teeth Ga with a torsional angle a of 30° or more by coldforging with a press.

Furthermore, as the speed gear W, a type forming helical teeth Ga havingcrowning Ca on the tooth flank (see FIG. 10 (D)) at the speed gearsection Pa was also adopted. But this crowning could not be formed bycold forging with a press.

SUMMARY OF THE INVENTION

In view of the problems inherent in conventional speed gears and theirmanufacturing methods, the object of the present invention is to providea speed gear having a speed gear section and a clutch spline sectionincluding speed gear teeth and an involute spline with a back taperhaving a chamfer at the tip, and a manufacturing method and apparatusfor the speed gear.

To achieve the objective, the speed gear according to the presentinvention has a speed gear section and a clutch spline sectionintegrally formed by forging. The clutch spline section is provided withan involute spline with a back taper having a chamfer at the tip. Speedgear teeth are formed by forging with rolling dies at the speed gearsection with reference to the clutch spline section forming the involutespline with a back taper.

The speed gear forming the subject of the present invention includes aspeed gear having helical teeth or flat teeth as the teeth of the speedgear.

Moreover, the speed gear forming the subject of the present inventionalso includes a speed gear having crowning on the tooth flank.

Furthermore, the speed gear forming the subject of the present inventionfurther includes a speed gear in which the tip diameter of the backtapered involute spline formed on the clutch spline section is largerthan the root diameter of the speed gear teeth formed on the speed gearsection and the clearance between the speed gear section and the clutchspline section is no more than 2 mm.

Further, the speed gear forming the subject of the present inventionincludes a speed gear in which an involute spline with a back taper isformed in a shape conformable to the tip shape of dies by pushing in thedies, radially disposed against the axial line of the gear among splineteeth parallel to the axial line of the gear formed by forging, towardthe center of gear in a direction perpendicular to the axial line of thegear.

The manufacturing method of the speed gear according to the presentinvention comprises integral molding, by either hot or warm forging, thespeed gear section and the clutch spline section, rough-forming speedgear teeth in the speed gear section and involute splines parallel tothe axial line of the gear in the clutch spline section, forming theinvolute splines parallel to the axial line of the gear formed on theclutch spline section by cold forging into an involute spline with aback taper having a chamfer at the tip, and then finish forming thespeed gear teeth formed at the speed gear section. The finish forming ofthe speed gear teeth is done by forming the speed gear teeth by rollingdies, by cold forging, while turning them around a shaft hole locatedwith reference to the clutch spline section forming the involute splinewith a back taper.

In this case, the manufacturing method may be constructed in a way toform crowning on the tooth flank of the speed gear teeth by means ofrolling dies.

Moreover, the forming of an involute spline with a back taper may beperformed by pushing in dies, radially disposed against the axial lineof the gear among spline teeth parallel to the axial line of the gearformed at the clutch spline section, toward the center of the gear inthe direction perpendicular to the axial line of the gear, in a shapeconformable to the tip shape of the dies.

The manufacturing apparatus of the speed gear according to the presentinvention, relating to the method of the present invention, comprises achuck for holding the shaft hole at the center of the work gear, a tailstock for turning the work gear through the chuck around its shaft hole,a synchronizing gear disposed in the tail stock that turns together withthe tail stock, a driven gear engaging with the synchronizing gear, anda rolling spindle on which are disclosed rolling dies. The work gear issubmitted to finish forming of the rough-formed speed gear teeth by therolling dies turning in synchronization with the work gear while turningthe work gear around its shaft hole through the synchronizing gear andthe driven gear.

In this case, the chuck may comprise a collet chuck and a male cone tobe inserted in the collet chuck so as to expand the diameter of thecollet chuck and hold the shaft hole at the center of the work gear.

Moreover, the rolling dies may be constructed to perform finish formingof helical rough-formed teeth.

Furthermore, the rolling dies may be constructed to also performcrowning at the tooth flank of the rough-formed speed gear teeth.

According to the present invention, it becomes possible to integrallyform, by forging, the speed gear section and the clutch spline sectionincluding speed gear teeth and an involute spline with a back taperhaving a chamfer at the tip, thus providing the following actions andeffects.

1. By forming speed change gear teeth and an involute spline with a backtaper having a chamfer at the tip by forging, it becomes possible toimprove the strength of the gear without cutting the metal flow of theteeth, avoiding an increase in manufacturing cost due to machining, andreducing the manufacturing cost of the speed gear.

2. It is easy to concentrically secure the clutch spline section formingan involute spline with a back taper with the speed gear section formingspeed gear teeth, enabling the manufacture of a highly-accurate speedgear.

3. When forming helical teeth as speed gear teeth, it is possible tomanufacture a highly-accurate speed gear, especially helical teeth witha torsional angle of 30° or more, by forging.

4. When forming speed gear teeth by forging, it is possible to alsoperform crowning at the tooth flank of the speed gear teeth at the sametime.

5. By forming an involute spline with a back taper having a chamfer atthe tip by forging, it becomes possible to not only manufacture ahighly-accurate speed gear without hooking due to machining, but to alsoobtain a speed gear with excellent shift feeling.

6. The absence of restrictions on the component materials of the speedgear enables the use of high-strength, difficult to cut steel, making itpossible to manufacture a compact speed gear easily.

7. It is possible to manufacture a speed gear with a shape difficult toachieve through machining, and obtain a compact speed gear.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory drawing showing a manufacturing process of aspeed gear according to the present invention.

FIG. 2 is a front sectional view of an apparatus for rough-forming agear used in the manufacture of the speed gear according to the presentinvention.

FIG. 3 is a front sectional view of an apparatus for forming an involuteshape used in the manufacture of the speed gear according to the presentinvention.

FIGS. 4(A) and 4(B) show a lower die of the apparatus for forming aninvolute shape, 4(A) being a plan view, and 4(B) a front elevation of amain part.

FIGS. 5 show dies of the apparatus for forming an involute shape, 5(A)being a plan view, 5(B) a partially broken front elevation, and 5(C) anexplanatory drawing of a die tip.

FIG. 6 is a front sectional view of a flow forming apparatus used forthe manufacture of the speed gear according to the present invention.

FIG. 7 is an expanded view of a main part of the flow forming apparatus.

FIG. 8 is an explanatory drawing showing the relation between asynchronizing gear and a driven gear.

FIG. 9 is an explanatory drawing showing the relation between rollingdies and an intermediate product.

FIGS. 10(A)-10(D) are explanatory drawings of various kinds of speedgears.

FIGS. 11(A)-11(C) show a typical speed gear, 11(A) being a sectionalview, 11(B) an exploded view of a main part, and 11(C) an expandedexplanatory drawing of teeth of the speed gear.

DETAILED DESCRIPTION OF THE INVENTION

Explanation will be given hereafter of an embodiment of a speed gear, amanufacturing method and an apparatus according to the presentinvention, based on the drawings.

First, a method for forming the speed gear of the present invention willbe explained by using FIG. 1, which concerns a case of forming of aspeed gear W of a shape as indicated in FIGS. 11(A) and 11(B).

First, a raw material suitable for the speed gear W to be manufacturedis cut to a prescribed length by means of a billet shear or a saw (FIG.1 (1), (2)). This raw material WO is heated to a temperature suitablefor either hot or warm forging (FIG. 1 (3)).

In this case, materials suitable for the speed gear W, such as SC steel,SCM steel, SNC steel, SNCM steel, SCR steel, etc., may be used as theraw material.

Moreover, the heating temperature may be set depending on the type offorging (hot or warm), the nature of the material, the shape, size,etc., at 1150° C. to 1200° C., for example.

After heating, the raw material W0 is submitted to a plural number ofprocesses to integrally form a speed gear section Pa and a clutch splinesection Pb and to form an intermediate product W4 having rough-formedspeed gear teeth Ra at the speed gear section Pa and rough-formedinvolute spline Rb at the clutch spline section Pb parallel to the axialline of the gear.

This hot forging process is usually composed, though not particularlyrestricted to such composition, of four processes, i.e. an upsettingprocess (FIG. 1 (4)), a blocker process (FIG. 1 (5)), a finisher process(FIG. 1 (6)) and a piercing process (FIG. 1 (7)).

Among those processes, the upsetting process (FIG. 1 (4)) is a processfor forming the raw material W0 into a shape easy for forging. Thematerial W1 which has passed through this process is submitted to theblocker process (FIG. 1 (5)) and the finisher process (FIG. 1 (6), to bedescribed in detail later) to be adjusted into the required generalshape and to have the required teeth rough-formed on the speed gearsection Pa and the clutch spline section Pb.

The blocker process (FIG. 1 (5)) and the finisher process (FIG. 1 (6))may be further composed of a plural number of processes, depending onthe nature of the material W1, the shape and size of the intermediateproduct W1 to be formed, etc.

The intermediate product W4 realized by forming a shaft hole H at thecenter of the intermediate product W3 is obtained with the piercingprocess (FIG. 1 (7)). The diameter of the shaft hole H is formed to beslightly smaller than the final finished dimension.

The intermediate product W4, having the required teeth rough-formed onthe speed gear section Pa and the clutch spline section Pb, aresubmitted, in a heat treating process (FIG. 1 (8)), to heat treatmentsuch as annealing, etc. In a shot blasting process (FIG. 1 (9)), scaleadhering to the surface of the intermediate product W4 is removed. In alubrication process (FIG. 1 (10)), required lubrication such as abonderite process, treatment by a molybdenum disulfide based lubricant,etc. will be performed to ensure smooth execution of the subsequent coldforging process.

The intermediate product W4 which has passed through the lubricationprocess (FIG. 1 (10)) will be submitted, in a cold coining process (FIG.1 (11)), to finish forming of involute spline Rb. Then, in an involutespline forming process (FIG. 1 (12), to be described in detail later),an involute spline Sb, parallel to the axial line of the gear and formedat the clutch spline section Pb, will be formed from the involute splineRb in a back tapered shape.

The intermediate product W6 which passed through the involute splineforming process (FIG. 1 (12)) will be submitted, in a machining process(FIG. 1 (13)), to lathe turning of the end face of the intermediateproduct W6, the inner circumferential surface of the shaft hole H andother parts, with reference to the clutch spline section Pb havinginvolute splines with back taper Gb formed with final finisheddimensions.

The intermediate product W7 which passed through the machining process(FIG. 1 (13)) will be passed on to a speed gear teeth forming process(FIG. 1 (14), to be described in detail later), where the speed gearteeth Ra formed at the speed gear section Pa are finish formed intospeed gear teeth while turning around the shaft hole H.

At that time, crowing Ca may be formed on the tooth flank of the speedgear teeth Ra.

The intermediate product W8 which passed through the speed gear teethforming process (FIG. 1 (14)) will be submitted, in the machiningprocess (FIG. 1 (15)), to lathe turning of the outer circumference, endface and other parts of the speed gear section Pa. Then, in a heattreating process (FIG. 1 (16)), required heat treatments such ascarbo-hardening, tempering, etc. are carried out. By further passing theintermediate product W8 through the grinding process (FIG. 1 (17)),speed gear W as a final product results.

Next, the finisher process (FIG. 1 (6)) will be described in detail.

The finisher process consists in integrally forming the speed gearsection Pa and the involute spline with back taper Pb on theintermediate product W2, provided in the required general shape by theblocker process (FIG. 1 (5)) of either a hot or warm forging process,rough-forming speed gear teeth Ra at the speed gear section Pa and roughforming involute spline Rb parallel to the axial line of the gear at theinvolute spline with back taper.

FIG. 2 indicates an example of an apparatus for rough-forming gear usedfor executing this finisher process.

This apparatus for rough-forming gear is designed to simultaneouslyrough-form helical teeth Ra as speed gear teeth at the speed gearsection Pa and involute spline Rb parallel to the axial line of the gearat the clutch spline section Pb. Its structure will be explainedhereafter.

A die mounting stand 31 is attached on a base 30, and a die 32 forforming gear is mounted on this die mounting stand 31.

The die 32, formed in a cylindrical shape, is provided, at its innercircumferential surface, with forming teeth 32 a corresponding to thehelical teeth Ra to be formed at the speed gear section Pa of theintermediate product W2.

Moreover, in the die 32 will be inserted, from above and belowrespectively, an upper punch 33 U and a lower punch 33 D, which produceplastic deformation by holding and pressing the intermediate product W2from above and below. In this case, the die 32 will be constructed insuch a way that, as the forming teeth 32 a of the die 32 and driventeeth 33 a formed at the outer circumference of the lower punch 33Dengage with each other and the lower punch 33D moves in the die 32, thelower punch 33D turns according to that amount of movement.

The upper and lower punches 33U, 33D are formed in a shape capable offorming the intermediate product W2 into the intermediate product W3 byproducing plastic deformation in the intermediate product W2 incollaboration with the die 32. The lower punch 33D is further provided,at its inner circumferential surface at the top, with forming teeth 33bcorresponding to the involute spline Rb parallel to the axial line ofthe gear to be formed at the clutch spline section Pa of theintermediate product W2.

The upper and lower punches 33U, 33D are rotatably supported throughupper and lower bearing plates 34U, 34D. The upper punch 33U is made togo up and down by means of a lifter 38 through upper punch mounting base37 while the lower punch 33D is made to go up and down by means of apiston 36 moving as hydraulic operating fluid is fed into a hydrauliccylinder 35.

The lower punch 33D, in which a lower knockout pin P1 is inserted, isoperated by a knockout pin P2 passing through the base 30, while theupper punch 33U, in which upper knockout pin P3 is inserted, is operatedby knockout pin P4 passing through the lifter 38.

Next, explanation will be given of the motions of this apparatus forrough-forming gear.

The intermediate product W2 is placed on the lower punch 33D and, as thelifter 38 is made to come down, the intermediate product W2 is held andpressed between the upper punch 33U and the lower punch 33D to produceplastic deformation, and rough-form helical teeth Rb at the speed gearsection Pa and involute spline Rb parallel to the axial line of the gearat the clutch spline section Pb at one time.

After that, hydraulic operating fluid is supplied into the hydrauliccylinder 35 to make the piston 36 go up and push up the lower punch 33D.In this case, the piston 36 is made to go up until the formedintermediate product W3 is detached from the gear die 32.

At that time, as the lower punch 33D moves in the gear die 32, the lowerpunch 33D turns in proportion to the amount of that movement, and theformed intermediate product W3 also turns at the same time, because theforming teeth 32 a of the gear die 32 are engaged with the driven teeth33 a formed on the outer circumferential surface of the lower punch 33D.This makes it possible to take out the intermediate product W3 withoutcausing damage to the helical teeth Ra and the involute spline Rbparallel to the axial line of the gear formed respectively at the speedgear section Pa and the clutch spline section Pb of the intermediateproduct W3.

To take out the intermediate product W3, the lifter 38 is made to up torelease the holding of the intermediate product W3 by the upper punch33U and the lower punch 33D. Then the piston 36 of the hydrauliccylinder 35 is made to go up to detach the helical teeth Ra formed atthe section of speed gear Pa of the intermediate product W3 from theforming teeth 32 a of the gear die 32. After that, the lower knockoutpin P1 is made to protrude by the knockout pin P2, and the upperknockout pin P3 is made to protrude by the knockout pin P4, to detachthe involute spline Rb from the forming teeth 33 b of the lower punch33D and release the intermediate product W3 from the upper and lowerpunches 33U, 33D.

Next, the involute spline forming process of FIG. 1 (12) will beexplained in detail.

The involute spline forming process consists in performing, in the coldcoining process (FIG. 1 (11)), finish forming of the involute spline Rbparallel to the axial line of the gear rough-formed at the clutch splinesection Pb, and then forming, on intermediate product W5, the involutespline parallel to the axial line of the gear formed at the clutchspline section Pb into the involute spline with back taper Gb.

FIG. 3 to FIG. 5 indicate an example of an apparatus for forming theinvolute spline used for this forming process.

An apparatus for forming an involute spline 1, designed to form aninvolute spline parallel to the axial line of the gear formed at theclutch spline section Pb into an involute spline with back taper Gb, isconstructed as explained hereafter.

An upper die 11 is disposed on an upper die mounting base 12 so as to beurged downwardly by a spring 12A.

A lower die 13 opposed to the upper die 11 is fixed on a lower diemounting base 14. A punch 15 is disposed on the lower die mounting base14 through the lower die 13. Outside the punch 15 is disposed a knockoutcylinder 16 of a cylindrical shape and operated with a knockout pin 20.A cylindrical case 17 is fixed to the lower die mounting base 14. On thecase 17 are formed, at a prescribed pitch, cam inserting holes 17Hagreeing with the angle between teeth and the number of teeth of theinvolute spline Gb for forming the involute spline Sb into the involutespline with back taper Gb. The outer side faces of these cam insertingholes 17H are formed into cam supporting faces 17F. Cams 21 are insertedin the cam inserting holes 17H, respectively.

The cams 21 inserted in cam inserting holes 17H are supported on thelower die mounting base 14 through a spring 24, being supported by acircular flange 18 operated by a knockout pin 19, and fixed to thiscircular flange 18 by means of a bolt 21V.

The length of a knockout pin 19 and the knockout pin 20 are set in sucha way that the knockout pin 20 pushes up the knockout cylinder 16 afterthe knockout pin 19 has pushed up the flange 18.

The cam 21, the back face of which is finished with high accuracy to bein sliding contact with the cam supporting face 17F of the case 17, hasa pin 22 on the inner side at its lower part projecting such that a topend of the pin 22 inclines inwardly. A die pressing face 21T has a tiltangle equal to the inclination of the pin 22 and is formed on the innerside face, facing the pin 22.

At the top of the lower die 13 are formed, as shown in FIG. 4, dieinserting holes 13H agreeing with the angle between teeth and the numberof teeth of the involute spline with back taper Gb, toward the center ofthe lower die 13.

The die inserting holes 13H have sections that are about circular andtops cut in a plane. In these die inserting holes 13H are inserted dies23 having sections that are about circular and having tops cut in aplane. This enables a construction in which the dies 23 are radiallydisposed toward the center of the lower die 13 while the case 17supports the flat part of the dies 23 to prevent turning of the dies 23.

A tip 23D of the die 23 is pressed against the involute spline Sbparallel to the axial line of the gear formed at the clutch splinesection Pb, producing plastic deformation, and thus changing the shapeinto a shape available for formation into the involute spline with backtaper. Moreover, in the die 23 is drilled a pin inserting hole 23H forinserting the pin 22. The rear end face 23T of the die 23 is formed intoan inclined face corresponding to the die pressing face 21T of the cam21.

Next, explanation will be given on the motions of this apparatus 1 forforming the involute spline.

The intermediate product W5 is placed on the lower die 13. As the upperdie mounting base 12 is made to come down, the intermediate product W5is held between the upper die 11 urged by the spring 12S and the lowerdie 13. The top face of the cam 21 is pressed by the upper die mountingbase 12, with a slight delay after the holding of the intermediateproduct W5.

As a result, the cam 21 and the flange 18 are pushed down, and the rearend face 23T of the die 23 is pressed by the die pressing face 21T ofthe cam 21 while the respective dies 23 slide in the direction towardthe center of the lower die 13, namely in the axial direction of theintermediate product W5. The involute splines Sb parallel to the axialline of the gear formed at the clutch spline section Pb are then formedinto involute splines with back taper Gb by the tips 23D of the dies 23.

After that, the upper die mounting base 12 is made to go up, to push upthe knockout pin 19 and make the flange 18 go up. This also makes thecam 21 go up but, since the pin 22 provided in projection with aninclination against the cam 21 is inserted in the pin inserting hole 23Hof the die 23, the respective dies 23 forcibly slide in the directionopposite to the center of the lower die 13, and the tip 23D of the die23 is detached from the intermediate product W6 on which is formed theinvolute spline with back taper Gb.

To take out the intermediate product W6, the tip 23D of the die 23,after being detached from the intermediate product W6 so that theinvolute spline with back taper Gb is not damaged by the tip 23D of thedie 23, pushes down the knockout pin 20 and makes the knockout cylinder16 protrude, thus releasing the intermediate product W6 from the lowerdie 13.

Next, the speed gear teeth forming process by the flow forming of FIG. 1(14) will be explained in detail.

The speed gear teeth forming process by flow forming consists in finishperforming, with the involute spline forming process of FIG. 1 (12),speed gear teeth Ra rough-formed at the speed gear section Pa into speedgear teeth Ga, while rotating the intermediate product W7 around theshaft hole H, with reference to the clutch spline section Pb havinginvolute spline with back taper Gb formed in the final finisheddimensions.

FIG. 6 to FIG. 9 show an example of the apparatus for flow forming usedfor executing the speed gear teeth forming process by flow forming.

An apparatus for flow forming 7, intended to finish form helical teethRa into helical teeth Ga, is constructed as described below.

The apparatus for flow forming 7 is composed of a tail stock unit 4alternately rotatable in normal and reverse directions, a chuck unit 5for holding the intermediate product W7 in collaboration with the tailstock unit 4, and a rolling die unit 6 driven by the rotation of thetail stock unit 4 for finish forming helical teeth Ra into helical teethGa.

The tail stock unit 4 is constructed by fixing a synchronizing gear 42,a receiving die 43 and a collet chuck 44 by means of a bolt 45 to thetip of the tail stock 41, which is alternately rotatable in normal andreverse directions.

The synchronizing gear 42 has teeth which protrude more than the tailstock 41. The teeth are in phase with the helical teeth Ga to be formed.

On the receiving die 43 is formed a concave part in the shape of aninvolute spline corresponding to the involute spline with back taper Gbformed at the clutch spline section Pb of the intermediate product W7.

The chuck unit 5 is constructed by fixing a clamp die 52 and a male cone54 to a chuck receiving base 51, disposed to face the tail stock unit 4with a bolt 55. A stripper 53 disposed at the outer circumference of theclamp die 52 is fastened to a rod 56.

As the chuck unit 5 is made to advance, the receiving die 43 of the tailstock unit 4, disposed face to face with the chuck unit 5, and the clampdie 52 of the chuck unit 5 hold the intermediate product W7 by engagingthe involute spline with back taper Gb formed at the clutch splinesection Pb of the intermediate product W7 in the concave part in theshape of an involute spline formed in the receiving die 43. This putsthe helical teeth Ra in phase with the synchronizing gear 42.

Moreover, the intermediate product W7 is held accurately around theshaft hold H of the intermediate product W7, because it is held as themale cone 54 of the chuck unit 5 is inserted in the collet chuck 44 ofthe tail stock unit 4, thus flaring a claw segment 44a of the colletchuck 44.

Furthermore, the stripper 53 is slidably disposed at the outercircumference of the clamp die 52 fixed to the chuck receiving base 51and fastened to the tip of the rod 56 passing through the chuckreceiving base 51 to slidably support a mounting base 57, to which thebase end of the rod 56 is fixed, in the axial direction of the chuckreceiving base 51.

The chuck unit 5 is constructed so as to release, after formation of thehelical teeth Ga, the holding of the intermediate product W8 by thereceiving die 43 and the clamp die 52 by making the chuck receiving base51 retreat by making the stripper 53 protrude by means of the rod 56.

The rolling die unit 6 is constructed of a movable carriage 61 whichtraverses against the tail stock 41, a rolling spindle 62 disposedparallel to the tail stock 41 through bearings 63, 63, a driven gear 64disposed in the rolling spindle 62 and engaging with the synchronizinggear 42, and a rolling die 65.

Next, the motions of this apparatus for flow forming 7 will beexplained.

As the chuck unit 5 is made to advance, the receiving die 43 of the tailstock unit 4, disposed face to face with the chuck unit 4, and the clampdie 52 of the chuck unit 5 hold the intermediate product W7. The movablecarriage 61 of the rolling die unit 6 traverses against the tail stock41 to engage the driven gear 64 with the synchronizing gear 42 andengage the rolling die 65 with the helical teeth Ra, rough-formed at thespeed gear section Pa of the intermediate product W7.

The intermediate product W7 and the chuck unit 5 are made to rotate byturning of the tail stock 41. In this case, the tail stock 41 preferablymakes normal rotation and reverse rotation alternately at prescribedcycles.

On the other hand, the rotation of the tail stock 41 is transmitted,through the synchronizing gear 42, the driven gear 64 and the rollingspindle 62, to the rolling die 65, and this rolling die 65 turns insynchronization with the synchronizing gear 42.

As a result, the intermediate product W7, which is engaged with therolling die 65, is turned by the tail stock 41. While the intermediateproduct W7 is turning with the rolling die 65, the helical teeth Ra arefinish formed into helical teeth Ga by forging with the rolling die 65.

To take out the intermediate product W8 on which helical teeth Ga areformed, the chuck receiving base 51 is made to retreat to cancel holdingof the intermediate product W8 by the receiving die 43 and the clamp die52. The intermediate product W8 fit in the clamp die 52 is inclined bymaking the stripper 53 protrude by means of the rod 56.

The speed gear and the manufacturing method and apparatus according tothe present invention have so far been explained, by taking, as anexample, the speed gear W of the form as indicated in FIGS. 11(A) and11(B), realized in a way to form helical teeth Ga as speed gear teeth atthe speed gear section Pa. The object of the present invention is notrestricted to a speed gear of this form, but may be modified as requiredwithin a range not deviating from its purport.

To be more concrete, the speed gear W forming the subject of the presentinvention includes a speed gear with flat teeth, in addition to speedgear having helical teeth, as speed gear teeth Ga, and further includesa speed gear having crowning Ca on the tooth flank of the speed gearwith Ga as shown in FIGS. 10(C) and 10(D) and also includes those nothaving crowning Ca, as a matter of course.

In this case, by suitably selecting the shape of the rolling die 65 ofthe apparatus for flow forming 7, when finish forming, by forging withrolling die 65, speed gear teeth Ra, rough-formed at the speed gearsection Pa of the intermediate product W7, into speed gear teeth Ga, itis possible to form crowning Ca on the tooth flank of the teth of speedgear Ga at the same time.

Moreover, a speed gear W forming the subject of the present inventionincludes speed gear in which the tip diameter Db of the back taperedinvolute spline Gb formed on the clutch spline section is larger thanthe root diameter Da of the speed gear teeth Ga formed on the speed gearsection Pa as indicated in FIG. 10(B). The clearance t of a groove Naformed between the speed gear section Pa and the clutch spline sectionPb is no more than 2 mm, as also in a speed gear in which a partition Nbis formed between the speed gear section Pa and the clutch splinesection Pb, as shown in FIG. 10(C), etc., which were difficult to workwithin a method of forming speed gear teeth Ga on the speed gear sectionPa by machining such as hobbing, etc. Speed gear in which the clearancet of the groove Na formed at the speed gear section Pa and the clutchspline section Pb is larger than 2 mm, as shown in FIG. 10(A), are alsoincluded, naturally.

What is claimed is:
 1. A manufacturing apparatus of speed gear,comprising a collet chuck and a male cone to be inserted in the colletchuck, so as to expand the diameter of the collet chuck, for holding ashaft hole pierced at a center of a work gear, a tail stock for turningthe work gear, through the collet chuck, around its shaft hole, asynchronizing gear disposed in the tail stock that turns together withthe tail stock, a driven gear engaging with the synchronizing gear, anda rolling spindle on which are disposed rolling dies, wherein the workgear has speed gear teeth, rough-formed in advance on a speed gearsection of the work gear, finish formed by the rolling dies turning insynchronization with the work gear, while turning the work gear aroundthe shaft hole, through the synchronizing and driven gears.
 2. Amanufacturing apparatus of speed gear as defined in claim 1, whereinsaid rolling dies are constructed in a way to perform finish forming ofhelical teeth rough-formed in advance at the section of speed gear ofthe work gear.
 3. A manufacturing apparatus of speed gear as defined inclaim 1, wherein said rolling dies are constructed in a way to alsoperform crowning at the tooth flank of the speed gear teeth rough-formedin advance at the speed gear section of the work gear.
 4. Amanufacturing apparatus of a speed gear for finish forming of speed gearteeth that have been rough-formed in advance on a work gear, saidmanufacturing apparatus comprising: a collet chuck having a male cone tobe inserted in said collet chuck for holding a shaft hole piercedthrough the center of the work gear by expanding the diameter of saidcollet chuck; a tail stock connected with said collet chuck for turningthe work gear through said collet chuck; a synchronizing gear disposedwith said tail stock so as to turn together with said tail stock; adriven gear for engagement with said synchronizing gear; a rollingspindle arranged to be rotated by said driven gear; and rolling dies,disposed with said rolling spindle so as to be turned by said rollingspindle, for engagement with the speed gear teeth that have beenrough-formed in advance on the work gear, such that when the work gearis held by said collet chuck and turned by the tail stock, and saiddriven gear engages with said synchronizing gear, said rolling dies areengaged with the speed gear teeth of the work gear and turned insynchronization with the work gear through said synchronizing and drivengears for finish forming of the speed gear teeth.
 5. The manufacturingapparatus of claim 4, wherein said rolling dies are constructed so as toperform finish forming of helical speed gear teeth that have beenrough-formed in advance at the speed gear section of the work gear. 6.The manufacturing apparatus of claim 4, wherein said rolling dies areconstructed so as to also perform crowning at tooth flanks of the speedgear teeth that have been rough-formed in advance at the speed gearsection of th work gear.